prof. rajesh bhagat - · pdf fileprof. rajesh bhagat asst. professor civil engg. department y....

Prof. Rajesh BhagatAsst. Professor

Civil Engg. Department

Y. C. C. E., Nagpur

Mobile No.:- 8483003474 / 8483002277

Email ID:- [email protected]

Website:- www.rajeysh7bhagat.wordpress.com

B. E. (Civil Engg.) M. Tech. (Environmental Engg.)

GCOE, Amravati VNIT, Nagpur

1) GATE Exam Qualified Two Times.

2) Junior Engineer, Z. P. Washim.

3) Lecturer , K.D.K. College of Engineering, Nagpur

4) Lecturer, P. R. Pote (Patil) College of Engg., Amravati.

5) Assistant Professor, P.C.E., Nagpur.

6) Assistant Professor, Cummins College of Engg. For Women, Nagpur.

7) Scientist, Council of Scientific & Industrial Research, India.

UNIT-I1. Introduction to Air Pollution.

2. Classification and Sources of Air Pollutants.

3. Effects of Air Pollutants on Man, Plants, Animal & Materials .

4. Atmosphere and Its Zones.

5. Air Pollution Episodes.

UNIT-II1. Meteorological parameters: Primary & secondary.

2. Atmospheric stability & plume behavior.

3. Air sampling and measurement.

UNIT-III1. Air Pollution Control: Industrial Air Pollution Controlling Devices,

Gravity Settling Chamber, Cyclone & Fabric Filter, Wet Scrubber &

Electrostatic Precipitator.

2. Gaseous Air Pollution Controlling Devices: Absorption, Adsorption &

Oxidation.

3. Automobile Exhaust.

4. Noise Pollution, Its Effects & Control.

Atmosphere:-

Insulating blanket protecting the earth.

Softens the intense light & heat of the sun.

Ozone layers acts as protecting umbrella that absorbs dangerous UV rays.

Atmosphere is bound to the earth by gravity.

As we go higher & higher, the characteristics & composition changes.

Atmosphere is divided into four sphere.

1. Troposphere

2. Stratosphere

3. Mesosphere

4. Thermosphere or Ionosphere

5

7

Atmosphere is divided into four sphere:-

1. Troposphere

2. Stratosphere

3. Mesosphere

4. Thermosphere or Ionosphere

Atmospheric Layers:-

Troposphere:-

Lowest gaseous layer of the atmosphere.

Region of weather & clouds.

Extends to a height of about 10 km from the earth.

Contains nearly 2/3 rd of total mass of the atmosphere.

Temperature drops with increase in altitude (6 OR 6.5 ° C /km- Wet & 10 ° C /km -

Dry)

Stratosphere:-

2nd layer of atmosphere above troposphere starting from 20km to 50km (30 km thick)

Free from violent weather changes so preferred by jet liners.

Temp. increase with altitude due to presence of ozone layer.

Layers of ozone is not uniform in thickness.(highest at equator & lowest at Poles)

Boundary that divides stratosphere from mesosphere is called the stratopause.

Mesosphere:-

Region where few energy release reaction occur.

Lapse rate is +ve (decrease in temp.)

Coldest layer of atmosphere.

This layer has no significance in air pollution.

14

Ionosphere:-

Thermosphere

Very high temp. 8700c over equator

1430c over north pole.

Highest & vastest zone of atmosphere.

Starting at 115km above the earth upto 600km.

Region beyond 600km is termed as exosphere.

15

Atmospheric stability:-

The resistance of the atmosphere to vertical motion or mixing.

Lapse rate :- (vertical temp. gradient)

Rate at which temp. changes with elevation is called lapse rate.

Lapse rate in a Dry Adiabatic Atmosphere is called DALR (100C/km) &

(WALR 60C/km).

Actual lapse rate is called Environmental Lapse Rate ie ELR may be greater or less

than the DALR.

ELR determines whether the air or atmosphere is stable or unstable.

If the air is unstable, the vertical movement of air is encouraged, & If the air is stable,

vertical movement of air is discouraged.

Super Adiabatic Lapse rate = Rate is more than DALR.

Inversion = -ve lapse rate.

16

Stability of atmosphere depending upon the vertical air temperature distribution :-

Very stable : Temperature increases with increase in altitude. This is a -ve lapse rate, or an

Inversion.

Stable : Environmental lapse rate is less than the dry adiabatic lapse rate, but temperature

decreases with altitude increase.

Neutral : Environmental lapse rate is the same as the dry adiabatic lapse rate.

Unstable : Environmental lapse rate is greater than the dry adiabatic lapse rate.

Very unstable : Environmental lapse rate is much greater than the dry adiabatic rate, and

is called super-adiabatic.

DTEL 17

Stability is the degree to which the atmosphere will support, tolerate, or suppress vertical

motions.

In a stable atmosphere, a parcel of air that is displaced upwards will tend to return to its

original level while in an unstable atmosphere, a parcel of air displaced upwards will

continue to rise.

Fig. 6.9 Lapse Rate (16)

Fig. 6.10 Lapse Rate (16)

19

ELRWALR

DALR

ELR

ELR

DALR

WALR

WALR

DALR

20

-----------

Lapse Rate Example

Que.1:- Assuming the surface temperature is 15°C at the surface of theearth, what is the temperature at 5510.5 m?

Take ELR = 6.49°C/km

Lapse Rate Example

Que.1:- Assuming the surface temperature is 15°C at the surface of the

earth, what is the temperature at 5510.5 m?

Take ELR = 6.49°C/km

Solution:

5510.5 m = 5.5105 km

For each km the temperature decreases by 6.49°c

So the temperature decreases: 5.5105 x 6.49 = 35.76°c

Original temp was 15°,

temp at 5.5105 km = 15°c - 35.76°c = -20.76°C

23

Plume refers to the path & extents of the air pollutants released from stack source

into the atmosphere. Depends on the vertical temp. & wind profile.

Plume Behavior are of six types :

1) Looping plumes

2) Coning plumes

3) Fanning plumes

4) Lofting plumes

5) Fumigation plumes

6) Trapping plumes

DTEL 25

Fanning plumes

form under very stable conditions. (extreme inversion condition)

spread out horizontally but do not mix vertically.

take place when the air temperature increases with altitude (inversion or –ve lapse rate).

The plume rarely reaches the grounds level unless the inversion is broken by surface heating

or the plume encounters a hill.

At night, with light winds and clear skies, fanning plumes are most probable.

Fig. 6.11 Fanning Plumes (16)

DTEL 26

Lofting plumes

form when there is a stable layer beneath unstable layer.

diffuse upward but not downwards and occur when there is a super-adiabatic layer above a

surface inversion.

generally not reach the ground surface.

a flat bottom and a rising top.

Fig. 6.12 Lofting Flumes (16)

DTEL 27

Looping plumes

take place when there has been a super-adiabatic lapse rate and solar heating. (Warm season)

Wavy character occurs in a highly unstable atmosphere bcoz of rapid mixing. (Day Time)

High turbulence disperse the plume rapidly but high conc. may occur close to the stack if

plume touches the ground.

Fig. 6.13 Looping Plumes (16)

DTEL 28

Coning plumes

Shaped like a cone roughly 100 with horizontal axis.

Coning plume gets resulted in when the vertical air temperature gradient has been between

dry adiabatic and isothermal, the air being slightly unstable with some horizontal and vertical

mixing occurring.

Coning is most likely to occur during cloudy or windy periods.

Fig. 6.14 Coning Plumes (16)

DTEL 29

Fumigation Plume

causes the high pollutant concentration plume reaching the ground level along the length of

the plume and is caused by a super-adiabatic lapse rate beneath an inversion.

The super-adiabatic lapse rate at the ground level occurs due to the solar heating.

This condition has been favored by clear skies and light winds.

Usually start when a fanning plume breaks up into a looping plume.

Fig. 6.15 Fumigating Plumes(16)

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Trapping:

In stable atmosphere both above & below stack with an unstable atmosphere in between

two inversion layer.

Diffuse only in the limited vertical height

Occur at any time of the day in any season.

33

Meteorology & Air Pollution:

Meteorology is the study and forecasting of weather changes resulting from large scale

atmospheric circulation

Meteorological parameter can trigger an air pollution episodes.

Once Pollutants Emitted:- Transported, Dispersed, Concentrated By meteorological

conditions.

Parameters can be classified into primary and secondary depending upon importance.

1. Wind Direction & Speed

2. Atmospheric Stability

3. Temperature

4. Mixing Height

5. Precipitation

6. Humidity

7. Solar Radiation

34

Wind Direction & Speed:-

Govern the drift & diffusion of air pollutants discharged.

Higher the wind speed at or near the point of discharge, the more rapidly will carry away

from the source and will disperse dilute with greater volume of air.

On the other hand, when wind speed are low pollutants tend to be concentrated near the

area of discharge for longer periods.

35

Temperature & Heat:-

Heat is the critical atmospheric variable.

Comes from the sun as a short wave radiation.

After striking the earth it losses energy & reradiates to the space as a long wave radiation.

Some of radiation absorbed by the atmosphere & temp. increases.

36

Atmospheric Stability:-

Ability to resists or enhance vertical motion.

Rate at which temp. changes is called lapse rate.

DALR = 10OC/Km & WALR = 6.5OC/Km (Neutral atmosphere)

Reverse or -ve lapse means Inversion.

During Inversion, vertical air movement is stopped & pollution will be concentrated

beneath the inversion layer.

37

Mixing Height:-

Height above the earth surface to which related pollutants will extend.

Primarily through the action of atmospheric turbulence.

Related to wind direction, wind speed & wind turbulence.

38

Precipitation:-

Cleansing action on the air pollutants discharged onto the atmosphere.

Removes the gaseous pollutants that are soluble in water.

Act as scrubbing fluid for the removal of air pollutants.

Thus it accelerates the deposition of pollutants on the ground.(water pollution & soil

Pollution)

39

Humidity:-

Measure of water vapour in atmosphere.

Always present in atmosphere & depends on temp.

Coastal regions & areas adjacent to huge water bodies are humid.

Moisture content of the atmosphere influence the corrosive action of air pollutants.

Also influence the potentiality for fog formation.

Humidity act as catalyst in the reaction of air pollutants like SO2, NO2, etc.

40

Solar Radiation:-

Depending on the location, solar radiation can have a pronounced effect on the type & rate

of chemical reaction in the atmosphere.

Photochemical smog formation at Los Angels is a typical example of the effect of solar

radiation on air pollution.

Stack Height & Effective Stack Height:-

• Height of the stack and the height of rise of the plume above the stack play a

major role in the ground level conc. expected on the down wind side.

• The plume Rise depends upon many factors such as exit velocity, wind speed,

diameter of stack, temp. of plume, lapse rate, etc.

41

H = h + Δh

Where, H – effective height if stack

h – Actual Height of stack

Δh – The Rise of Plume

There are several formulae are available to calculate the stack height.

As per Emission regulation published by the central board for prevention and control of pollution, New Delhi, The chimney height is to be calculated according to the formulae.

PM :- H = 74 (Q) 0.27

Where, Q = Particulate Matter Emission in Tonnes per Hour.

h = Height of Chimney in meters.

Gaseous Pollutants :- H = 14 (Q) 0.3

Where, Q = Gaseous Emission in Kg per Hour.


44

Que. 1: A factory uses 2,00,000 liters of furnace oil per month. If for one million

liters of oil used per year, the particulate matter emitted is 3.0 tonnes per year,

SO2 emitted is 59.7 tonness per year, NOx emitted is 7.5 tonnes per year,

Hydrocarobns emitted are 0.37 tonnes per year and CO emitted is 0.52 tonnes per

year, calculate the height of the chimney required to be provided for safe

dispersion of the pollutants.

Consumption of oil = 2,00,000 x 12 = 24,00,000 L/Year = 2.4 Million L/Year

Particulate Emission per million Liters per Year = 3.0 Tonnes/Year

Total Particulate Emission (Q) = 2.4 x 3.0 = 7.2 Tonnes/Year

45










SO2 Emission per million Liters per Year = 59.7 Tonnes/Year

Total SO2 emission, Q = 2.4 x 59.7 = 144 Tonnes/Year = 20 Kg/Hr

46










PM :- h = 74 (Q) 0.27

Where, Q = Particulate Matter Emission in Tonnes per Hour.


47

Assuming Working Days = 300 Days

Assuming Working Hours per Day = 24 Hours

Total Particulate Emission (Q) = ((7.2)/(300x 24)) = 0.001Tonnes/Hour

PM :- h = 74 (Q) 0.27

h = 74 (0.001)0.27

h = 11.47 m

48

Gaseous Pollutants :-

SO2 :- h = 14 (Q) 0.3

Q = SO2 Emission in kg/Hr

49

SO2 :- h = 14 (Q) 0.3


Q = 2.4 x 59.7 = 144 Tonnes/Year = 20 Kg/Hr

50

SO2 :- h = 14 (Q) 0.3



h = 14 (20)0.3

h = 34.4 m

Therefore adopt a height of 34.4 m (whichever is max.)

51

SO2 :- h = 14 (Q) 0.3



h = 14 (20)0.3

h = 34.4 m

Therefore adopt a height of 34.4 m (whichever is max.)

Note :- Since the emission of SO2 is much more than that of NOx, CO2, CO &

Hydrocarbons, the calculation of stack height is done based on SO2 emission data only

52

Effective Height of stack:-

H = h + Δh

Where, H – effective height if stack

h – Actual Height of stack

Δh – The Rise of Plume

Holland’s equation :-

Δh = ((vs x d)/u) (1.5 + 2.68 x 10-3 x p x d ((Ts – Ta)/Ts))

Where, p = Atmospheric pressure in millibars

Ts = Stack temp. in OK

Ta = Air Temp. in OK

Vs = Stack Gas Velocity

d = Diameter of Stack in m

u = wind Velocity in m/s

53

Que 2 :- Calculate the effective stack height for following data:-

Physical Stack = 203 m tall with 1.07 m in side diameter

Wind velocity = 3.56 m/s

Air Temp = 13 OC

Barometric Pressure = 1000 millibars

Stack gas velocity = 9.14 m/s

Stack gas temp. = 149OC

54


Physical Stack = 203 m tall = h

Side diameter = 1.07 m = d

Wind velocity = 3.56 m/s = u

Air Temp = 13 OC = Ta

Barometric Pressure = 1000 millibars = p

Stack gas velocity = 9.14 m/s = Vs

Stack gas temp. = 149OC = Ts

Temperature :-

Ts = 149OC + 273 = 422 OK

Ta = 13OC + 273 = 283 OK

55






Barometric Pressure = 1000 millibars = ρ



Temperature :-

Ts = 149 + 273 = 422 OK

Ta = 13OC + 273 = 283 OK

Holland’s Equation :-


56









Temperature :-

Ts = 149 + 273 = 422 OK

Ta = 13OC + 273 = 283 OK



Δh = ((9.14 x 1.07)/3.56) (1.5 + 2.68 x 10-3 x 1000 x 1.07 ((422 – 286)/422s))

Δh = 5.92 m

57









Temperature :-

Ts = 149 + 273 = 422 OK

Ta = 13OC + 273 = 283 OK


Δh = ((vs x d)/u) (1.5 + 2.68 x 10-3 x ρ d ((Ts – Ta)/Ts))

Δh = ((9.14 x 1.07)/3.56) (1.5 + 2.68 x 10-3 x 1000 x 1.07 ((422 – 286)/422s))

Δh = 5.92 m (Rise of Plume )

H = h + Δh = 203 + 5.92 = 208.92 m (Effective Height of stack)

58

Air Pollution Indices or Index (API)

1) It is system in which one can explain the quality of air to common man.

2) It is a scheme that transforms values of individual air pollution parameters into a single

number.

3) Technical terms may not be known to public.

4) There must be easiest, understanding & simplified way to define quality of ambient air.

5) Criteria for Index:-

1) Easily understand by public

2) Include major air pollutants

3) Calculated in simpler manner

4) Based on scientific data

5) Meaningful

6) Relate to ambient air quality standards & goals

7) Can be forecasted a day in advance

59

Air Pollution Indices or Index

API = ¼ (Cspm / Sspm +CNOx / SNOx + CSO2 / SSO2 + CCO / SCO) x 100

API =¼ (180.2 / 200 +98.5 / 80 + 19.9 / 80 + 2.55 / 20) x 100

API = 89.84 ~ 90

60

Air Pollution Indices or Index

Index Value Remark

0-25 Clean Air

26-50 Light Air pollution

51-75 Moderate Air Pollution

76-100 Heavy Air Pollution

>100 Severe Air Pollution

61

Other Rating:- Good, Acceptable, Satisfactory, Unsatisfactory, Unhealthy, Light Moderate, Heavy, Normal, Severe, etc.

Wind Roses:-

1) Wind roses shows the prevailing direction of wind.

2) Defined as any diagram to show the distribution of wind direction experienced at a

given location, over a considerable period.

3) Wind data ie Direction, duration, & intensity are graphically represented by a diagram

called Wind Rose.

Wind Roses:-

1) For accurate estimation of the dispersion of air pollutants in the atmosphere a

knowledge of the frequency distribution of wind direction as well as wind speed is

essential.

2) This type of information varies from city to city and varies for given city from month to

month.

3) Wind data should be collected for a period of atleast 5 years and preferably of 1o years,

so as to obtain an avg. data with sufficient accuracy.

Wind Rose Construction:-

1) The most common form consist of circle from which eight or sixteen lines emerge, one

for each direction.

2) Length of each line is proportional to the frequency of wind from that direction and

frequency of calm conditions is entered in the entre.

3) There are many variation in the construction of wind roses. Some indicates the range of

wind speeds from each direction & some relates wind direction with other

meteorological condition.

4) Line or bar extending to the north on the wind rose indicates the frequency of winds

blowing from the north.

5) Wind rose diagram is prepared using an appropriate scale to represent % frequencies of

wind direction and appropriate index shades, lines, etc. to represent various wind

speeds.

6) Observation corresponding to wind speed below 1Km/Hr are recorded as Calm.

Special Pollution Wind roses are:-

1) Precipitation Wind Rose

2) Smoke Wind Rose

3) SO2 Wind Rose

4) HC Wind Rose

70

SUMMARY

1) Explain various zones of atmosphere by giving the details of temperature variation & gases present

in each zone?

2) Explain with sketch the temperature variation with height in atmosphere and its impact on air

pollution?

3) What are meteorological parameters and how they affect air pollution? Explain the effect of speed

and wind direction?

4) What do you understand by Atmospheric Stability? Explain how atmospheric stability affects

dispersion of pollutants. Also explain variation in atmospheric stability with temperature profile?

5) What is lapse rate? State and explain various types of lapse rate with temperature profile? Also state

the atmospheric stability for each lapse rate?

6) Write a note on Plume Behavior under different atmospheric conditions or meteorological

conditions?

TYPICAL QUESTIONS

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